The demand for new types of electronic displays, such as LCD-based displays, has resulted in a continuing need for improvements to the technologies incorporated into these devices. For example, in conventional LCD backlight units (BLU), light is extracted from the light guide at a high angle and multiple diffusers and turning (brightness enhancing) films are used to achieve the desired angular emission required for the display. These films not only add cost, light loss, and system complexity, but also suffer from a number of material deficiencies that make them less than ideal for electronics. Current polymethylmethacrylate (PMMA) light guides have high transparency, but suffer from poor moldability, which limits use in small devices, and have high moisture absorption, leading to undesirable mechanical performance in large sizes (e.g., warp and material swelling). Other polymers, polycarbonate (PC) and cyclic olefin copolymer (COP), are typically used in handheld devices due to better moldability and less moisture absorption, but suffer from high light attenuation.
Further, even if the material, technological and engineering difficulties of current designs for backlight extraction are overcome, these polymeric materials are not idea for next generation, transparent displays as they are opaque. There is clearly a need for an improved backlight with high transparency which also emits light nearly perpendicular to the light guide as this would not only enable transparent displays, but could also simplify the BLU stack in conventional displays. The disclosed glass sheets provide these advantages and have better attenuation than PC and COP while maintaining good mechanical performance attributes, such as low CTE, low- to no-water absorption, and higher dimensional stability.